C6 Traction Control Issue

I am trying to help someone with a 05 C6 A4 that has different size wheels/tires than stock. The research I've done is that with the stock wheels/tires, the rears are 1.5" taller than the fronts. With the combo he's running now, the rears are .2" smaller than the fronts. This is causing the Traction Control to activate when at highway speeds. Right now, he is putting the car in Comp Mode everytime he starts the car to avoid the problem. Is there any fix for this? Before I spend the money to license the car, I need to see if there is a fix for this in the PCM. My gut feeling is this is a BCM issue or some other module that is sensing the wheel speed sensors, thinking traction is lost because the rear wheels are now truning faster than the fronts

Just need to correct the speedo file for the correct size tires.